Pixel circuit, its driving method, light-emitting diode display panel, and display device

Cross-reference to related application applications

The present application is the U.S. National Phase of PCT Application No. PCT/CN2015/070152 filed on Jan. 6, 2015, which claims a priority of the Chinese patent application No. 201410505051.X filed on Sep. 26, 2014, which is incorporated herein by reference in its entirety.

Technical field

The present disclosure relates to the field of display technology, in particular to a pixel circuit, its driving method, a light-emitting diode (LED) display panel, and a display device.

Background

Active matrix/organic light-emitting diode (AMOLED) display has currently become one of the hotspots in the research field of a flat-panel display. As compared with a liquid crystal display, the OLED has such advantages as low power consumption, low production cost, self luminescence, wide viewing angle and rapid response, so it has replaced the traditional liquid crystal display in display devices such as mobile phones, personal digital assistants (PDAs) and digital cameras. The design of a pixel driver circuit, as a core technology for the AMOLED display, is of very important significance.

Different from a thin film transistor (TFT)-LCD where a stable voltage is used to control the brightness, the OLED is driven by a current, so the stable current is required to control the light emission. Due to limitations of the manufacture process and the aging of elements, a threshold voltage (V.sub.th) of a driving TFT for each pixel may be drifted, and the current flowing through the OLED of each pixel may be changed along with the threshold voltage. As a result, uneven display brightness will occur, and an image display effect will be adversely affected.

Because a fingerprint of each person is unique, it is able to remarkably improve the system security through a fingerprint identification technique, and this technique will fit well in security protection or high-end consumer electronic products.

Hence, how to integrate a touch in-cell technique and an AMOLED technique with the fingerprint identification technique will certainly be a new trend for the display technology.

Summary

An object of the present disclosure is to provide a pixel circuit, its driving method, an LED display panel, and a display device, so as to improve the brightness evenness of the LED display panel as well as an image display effect of the display device, thereby to achieve the integration of display driving, fingerprint identification and touch detection in an effective manner.

In one aspect, the present disclosure provides in one embodiment a pixel circuit including an LED, a cathode of which is connected to a first signal source. The pixel circuit further includes: a display driving module connected to a first scanning line, a second scanning line, a control line, a data line, a second signal source, a third signal source and an anode of the LED, and configured to, under the control of a first scanning signal from the first scanning line, a second scanning signal from the second scanning line and a control signal from the control line, compensate for a threshold voltage of a driving transistor using a data signal from the data line and a second signal from the second signal source, so that a light-emitting driving signal for the LED is irrelevant to the threshold voltage of the driving transistor; and a fingerprint identification module connected to the first scanning line, the second scanning line, a fourth signal source and a signal read line, and configured to, under the control of the first scanning signal from the first scanning line and the second scanning signal from the second scanning line, identify a fingerprint and detect a touch.

Alternatively, the display driving module includes a first TFT, a second TFT, a third TFT, a fourth TFT, a fifth TFT, a first storage capacitor, and a first driving transistor. A first electrode of the first TFT is connected to the second signal source and a first end of the first storage capacitor, a gate electrode thereof is connected to the control line, and a second electrode thereof is connected to a first electrode of the first driving transistor. A first electrode of the second TFT is connected to the first electrode of the first driving transistor, a gate electrode thereof is connected to the second scanning line, and a second electrode thereof is connected to a second end of the first storage capacitor. A first electrode of the third TFT is connected to the third signal source, a gate electrode thereof is connected to the first scanning line, and a second electrode thereof is connected to the second end of the first storage capacitor. A first electrode of the fourth TFT is connected to the data line, a gate electrode thereof is connected to the second scanning line, and a second electrode thereof is connected to a second electrode of the first driving transistor. A first electrode of the fifth TFT is connected to the second electrode of the first driving transistor, a gate electrode thereof is connected to the control line, and a second electrode thereof is connected to the anode of the LED. A gate electrode of the first driving transistor is connected to the second end of the first storage capacitor.

Alternatively, the display driving module includes a sixth TFT, a seventh TFT, an eighth TFT, a second storage capacitor, a second driving transistor and a third driving transistor. A first electrode of the sixth TFT is connected to the data line, a gate electrode thereof is connected to the second scanning line, and a second electrode thereof is connected to a first electrode of the second driving transistor. A first electrode of the seventh TFT is connected to a second end of the second storage capacitor, a gate electrode thereof is connected to the first scanning line, and a second electrode thereof is connected to the third signal source. A first electrode of the eighth TFT is connected to a second electrode of the third driving transistor, a gate electrode thereof is connected to the control line, and a second electrode thereof is connected to the anode of the LED. A gate electrode and a second electrode of the second driving transistor are connected to the second end of the second storage capacitor. A first electrode of the third driving transistor is connected to a first end of the second storage capacitor and the second signal source, and a gate electrode thereof is connected to the second end of the second storage capacitor.

Alternatively, the fingerprint identification module includes a resetting transistor, an amplifying transistor, a switching transistor, a third storage capacitor and a detection electrode. A first electrode of the resetting transistor is connected to the fourth signal source, a gate electrode thereof is connected to the first scanning line, and a second electrode thereof is connected to a second end of the third storage capacitor. A first electrode of the amplifying transistor is connected to the fourth signal source, a gate electrode thereof is connected to the second end of the third storage capacitor, and a second electrode thereof is connected to a first electrode of the switching transistor. A gate electrode of the switching electrode is connected to the second scanning line, and a second electrode thereof is connected to the signal read line. A first end of the third storage capacitor is connected to the second scanning line. The detection electrode is connected to the second end of the third storage capacitor.

Alternatively, the transistors are P-type transistors, the first electrodes are source electrodes, and the second electrodes are drain electrodes.

Alternatively, a first signal from the first signal source is a low level signal or a zero-potential signal, the second signal from the second signal source is a high level signal, a third signal from the third signal source is a low level signal, and a fourth signal from the fourth signal source is a signal with a fixed potential.

Alternatively, the LED is an organic LED.

In another aspect, the present disclosure provides in one embodiment a method for driving the above-mentioned pixel circuit, including steps of: under the control of a first scanning signal from a first scanning line, a second scanning signal from a second scanning line and a control signal from a control line, compensating for a threshold voltage of a driving transistor using a data signal from a data line and a second signal from a second signal source, so that a light-emitting driving signal for an LED is irrelevant to the threshold voltage of the driving transistor; and under the control of the first scanning signal from the first scanning line and the second scanning signal from the second scanning line, identifying a fingerprint and detecting a touch.

Alternatively, the step of, under the control of the first scanning signal from the first scanning line, the second scanning signal from the second scanning line and the control signal from the control line, compensating for the threshold voltage of the driving transistor using the data signal from the data line and the second signal from the second signal source, so that the light-emitting driving signal for the LED is irrelevant to the threshold voltage of the driving transistor includes: at a first stage of a time period, enabling a third TFT to be in an on state, and enabling a first TFT, a second TFT, a fourth TFT and a fifth TFT to be in an off state, thereby enabling a second end of a first storage capacitor to be at a potential of a third signal from a third signal source; at a second stage of the time period, enabling the second TFT, the fourth TFT and a first driving transistor to be in the on state, and enabling the first TFT, the third TFT and the fifth TFT to be in the off state, thereby charging, by the data signal from the data line, the second end of the first storage capacitor to be at a potential equal to a difference between a potential of the data signal and a threshold voltage of the first driving transistor; and at a third stage of the time period, enabling the first TFT and the fifth TFT to be in the on state, and enabling the second TFT, the third TFT and the fourth TFT to be in the off state, thereby determining the light-emitting driving signal for the LED based on the data signal and the second signal, and driving the LED to emit light using the light-emitting driving signal.

Alternatively, the step of, under the control of the first scanning signal from the first scanning line, the second scanning signal from the second scanning line and the control signal from the control line, compensating for the threshold voltage of the driving transistor using the data signal from the data line and the second signal from the second signal source, so that the light-emitting driving signal for the LED is irrelevant to the threshold voltage of the driving transistor includes: at the first stage of the time period, enabling a seventh TFT to be in the on state, and enabling the sixth TFT and the eighth TFT to be in the off state, thereby enabling a second end of a second storage capacitor to be at the potential of the third signal from the third signal source; at the second stage of the time period, enabling the sixth TFT and a second driving transistor to be in the on state, and enabling the seventh TFT and the eighth TFT to be in the off state, thereby charging, by the data signal from the data line, the second end of the second storage capacitor to be at a potential equal to a difference between the potential of the data signal and a threshold voltage of the second driving transistor; and at the third stage of the time period, enabling the eighth TFT to be in the on state, and enabling the sixth TFT and the seventh TFT to be in the off state, thereby determining the light-emitting driving signal for the LED based on the data signal and the second signal, and driving the LED to emit light using the light-emitting driving signal.

Alternatively, the step of, under the control of the first scanning signal from the first scanning line and the second scanning signal from the second scanning line, identifying the fingerprint and detecting the touch includes: at the first stage of the time period, enabling a resetting transistor to be in the on state, and enabling a switching transistor to be in the off state, thereby enabling a second end of a third storage capacitor to be at a potential of a fourth signal from a fourth signal source; at the second stage of the time period, enabling the resetting transistor to be in the off state, enabling the switching transistor to be in the on state, enabling an amplifying transistor to be in the on or off state based on the potential at the second end of the third storage capacitor, thereby enabling a signal read line to transmit a signal corresponding to the state of the amplifying transistor, and enabling a processor connected to the signal read line to identify the fingerprint based on the signal from the signal read line; and at the third stage of the time period, enabling the resetting transistor, the switching transistor and the amplifying transistor to be in the off state.

Alternatively, at the second stage, the method further includes: determining information about a position for a fingerprint identification operation based on information about the second scanning line and the signal read line.

Alternatively, at the first stage, the first scanning signal is a low level signal, the second scanning signal is a high level signal, the control signal is a high level signal, and the data signal is a low level signal or a high level signal; at the second stage, the first scanning signal is a high level signal, a second scanning signal is a low level signal, the control signal is a high level signal, and the data signal is a high level signal; and at the third stage, the first scanning signal is a high level signal, the second scanning signal is a high level signal, the control signal is a low level signal, and the data signal is a low level signal.

In yet another aspect, the present disclosure provides in one embodiment an LED display panel including the above-mentioned pixel circuit.

In still yet another aspect, the present disclosure provides in one embodiment a display device including the above-mentioned LED display panel.

According to the pixel circuit, its driving method, the LED display panel and the display device in the embodiments of the present disclosure, the display driving module is connected to the first scanning line, the second scanning line, the control line, the data line, the second signal source, the third signal source and the anode of the LED, and configured to, under the control of the first scanning signal from the first scanning line, the second scanning signal from the second scanning line and the control signal from the control line, compensate for the threshold voltage of the driving transistor using the light-emitting driving signal for the LED, so that the light-emitting driving signal for the LED is irrelevant to the threshold voltage of the driving transistor; and the fingerprint identification module is connected to the first scanning line, the second scanning line, the fourth signal source and the signal read line, and configured to, under the control of the first scanning signal from the first scanning line and the second scanning signal from the second scanning line, identify the fingerprint and detect the touch. As a result, it is able to improve the brightness evenness of the LED display panel as well as the image display effect of the display device, thereby to achieve the integration of the display driving, the fingerprint identification and the touch detection in an effective manner.

Brief description of the drawings

FIG. 1 is a schematic view showing a pixel circuit according to one embodiment of the present disclosure;

FIG. 2 is a schematic view showing a display driving module of the pixel circuit according to one embodiment of the present disclosure;

FIG. 3 is a sequence diagram of signals involved in the pixel circuit according to one embodiment of the present disclosure;

FIG. 4 is a schematic view showing a state of the pixel circuit at a first stage according to one embodiment of the present disclosure;

FIG. 5 is a schematic view showing a state of the pixel circuit at a second stage according to one embodiment of the present disclosure;

FIG. 6 is a schematic view showing a state of the pixel circuit at a third stage according to one embodiment of the present disclosure;

FIG. 7 is another schematic view showing the display driving module of the pixel circuit according to one embodiment of the present disclosure;

FIG. 8 is another sequence diagram of the signal involved in the pixel circuit according to one embodiment of the present disclosure;

FIG. 9 is another schematic view showing the state of the pixel circuit at the first stage according to one embodiment of the present disclosure;

FIG. 10 is another schematic view showing the state of the pixel circuit at the second state according to one embodiment of the present disclosure;

FIG. 11 is another schematic view showing the state of the pixel circuit at the third stage according to one embodiment of the present disclosure;

FIG. 12 is a schematic view showing the principle for fingerprint identification of the pixel circuit according to one embodiment of the present disclosure;

FIG. 13 is another schematic view showing the principle for fingerprint identification of the pixel circuit according to one embodiment of the present disclosure; and

FIG. 14 is a schematic view showing the distribution of the pixel circuits according to one embodiment of the present disclosure.

Detailed description

In order to make the objects, the technical solutions and the advantages of the present disclosure more apparent, the present disclosure will be described hereinafter in a clear and complete manner in conjunction with the drawings and embodiments. Obviously, the following embodiments are merely a part of, rather than all of, the embodiments of the present disclosure, and based on these embodiments, a person skilled in the art may obtain the other embodiments, which also fall within the scope of the present disclosure.

Unless otherwise defined, any technical or scientific term used herein shall have the common meaning understood by a person of ordinary skills. Such words as “first” and “second” used in the specification and claims are merely used to differentiate different components rather than to represent any order, number or importance. Similarly, such words as “one” or “one of” are merely used to represent the existence of at least one member, rather than to limit the number thereof. Such words as “connect” or “connected to” may include electrical connection, direct or indirect, rather than to be limited to physical or mechanical connection. Such words as “on”, “under”, “left” and “right” are merely used to represent relative position relationship, and when an absolute position of the object is changed, the relative position relationship will be changed too.

The present disclosure provides in one embodiment a pixel circuit which, as shown in FIG. 1 , may include an OLED, a cathode of which is connected to a first signal source.

As shown in FIG. 1 , the pixel circuit may further include: a display driving module 1 connected to a first scanning line Scan 1 , a second scanning line Scan 2 , a control line EM, a data line, a second signal source, a third signal source and an anode of the OLED, and configured to, under the control of a first scanning signal V.sub.Scan1 from the first scanning line, a second scanning signal V.sub.Scan2 from the second scanning line and a control signal V.sub.EM from the control line, compensate for a threshold voltage V.sub.th of a driving transistor using a data signal V.sub.data from the data line and a second signal V.sub.dd from the second signal source, so that a light-emitting driving signal I.sub.OLED for the OLED is irrelevant to the threshold voltage V.sub.th of the driving transistor; and a fingerprint identification module 2 connected to the first scanning line, the second scanning line, a fourth signal source and a signal read line, and configured to, under the control of the first scanning signal V.sub.Scan1 from the first scanning line and the second scanning signal V.sub.Scan2 from the second scanning line, identify a fingerprint and detect a touch.

In the above embodiment, a first signal from the first signal source may be a low level signal, or the ground may serve as the first signal source so as to input a zero potential. The second signal V.sub.dd from the second signal source may be a high level signal, a third signal V.sub.int from the third signal source may be a low level signal, and a fourth signal from the fourth signal source may be a signal with a fixed potential, e.g., a common electrode signal Vcom.

The present disclosure further provides in one embodiment a method for driving the above-mentioned pixel circuit, which includes steps of: under the control of the first scanning signal V.sub.Scan1 from the first scanning line, the second scanning signal V.sub.Scan2 from a second scanning line and the control signal V.sub.EM from the control line, compensating for the threshold voltage V.sub.th of the driving transistor using the data signal V.sub.data from the data line and the second signal V.sub.dd from the second signal source, so that the light-emitting driving signal I.sub.OLED for the OLED is irrelevant to the threshold voltage V.sub.th of the driving transistor; and under the control of the first scanning signal V.sub.Scan1 from the first scanning line and the second scanning signal V.sub.Scan2 from the second scanning line, identifying a fingerprint and detecting a touch.

According to the pixel circuit and its driving method in the embodiments of the present disclosure, it is able to eliminate an effect of the threshold voltage V.sub.th of the driving transistor on the light-emitting driving signal I.sub.OLED, thereby to improve the brightness evenness of the OLED display panel as well as the image display effect of the display device. In addition, through a circuit structure where the control signal is multiplexed, it is able to achieve the display driving and the fingerprint identification simultaneously, thereby to achieve the integration thereof in an effective manner.

In one embodiment, as shown in FIG. 2 , the display driving module 1 may include a first TFT T 1 , a second TFT T 2 , a third TFT T 3 , a fourth TFT T 4 , a fifth TFT T 5 , a first storage capacitor C 1 , and a first driving transistor DTFT 1 . A first electrode of the first TFT T 1 is connected to the second signal source and a first end of the first storage capacitor C 1 , a gate electrode thereof is connected to the control line EM, and a second electrode thereof is connected to a first electrode of the first driving transistor DTFT 1 . A first electrode of the second TFT T 2 is connected to the first electrode of the first driving transistor DTFT 1 , a gate electrode thereof is connected to the second scanning line, and a second electrode thereof is connected to a second end of the first storage capacitor C 1 . A first electrode of the third TFT T 3 is connected to the third signal source, a gate electrode thereof is connected to the first scanning line, and a second electrode thereof is connected to the second end of the first storage capacitor C 1 . A first electrode of the fourth TFT T 4 is connected to the data line, a gate electrode thereof is connected to the second scanning line, and a second electrode thereof is connected to a second electrode of the first driving transistor DTFT 1 . A first electrode of the fifth TFT T 5 is connected to the second electrode of the first driving transistor DTFT 1 , a gate electrode thereof is connected to the control line EM, and a second electrode thereof is connected to the anode of the OLED. A gate electrode of the first driving transistor DTFT 1 is connected to the second end of the first storage capacitor C 1 .

The transistors included in the display driving module 1 and the fingerprint identification module 2 may be P-type transistors, so as to manufacture these transistors by an identical process, thereby to improve the yield of the display device. The first electrode of each transistor may be a source electrode, and the second electrode thereof may be a drain electrode.

The state of the display driving module 1 in FIG. 2 driven by the above method will be described hereinafter in conjunction with the sequence diagram as shown in FIG. 3 .

At a first stage, the display driving module 1 in FIG. 2 may be at a resetting stage. FIG. 3 shows at Stage 1 the signals. To be specific, the control signal V.sub.EM may be a high level signal, the first scanning signal V.sub.Scan1 may be a low level signal, the second scanning signal V.sub.Scan2 may be a high level signal, and the data signal V.sub.data may be a low level signal, so as to enable the third TFT T 3 to be in the on state, and enable the first TFT T 1 , the second TFT T 2 , the fourth TFT T 4 and the fifth TFT T 5 to be in the off state. As shown by a solid arrow in FIG. 4 , the third signal V.sub.int from the third signal source is transmitted to the second end of the first storage capacitor C 1 , i.e., node B, and the gate electrode of the first driving transistor DTFT 1 through the third TFT T 3 which is in the on state, so as to enable the second end of the first storage capacitor C 1 to be at a potential of the third signal V.sub.int, i.e., V.sub.B=V.sub.int. In the embodiments of the present disclosure, the third signal V.sub.int may be a low level signal, so the second end of the first storage capacitor C 1 is reset.

At a second stage, the display driving module 1 in FIG. 2 may be at a discharging and compensation stage. FIG. 3 shows at stage 2 the signals. To be specific, the control signal V.sub.EM may be a high level signal, the first scanning signal V.sub.Scan1 may be a high level signal, the second scanning signal V.sub.Scan2 may be a low level signal, and the data signal V.sub.data may be a high level signal, so as to enable the second TFT T 2 and the fourth TFT T 4 to be in the on state, and enable the first TFT T 1 , the third TFT T 3 and the fifth TFT T 5 to be in the off state. The gate electrode of the first driving transistor DTFT 1 is at the potential of the third signal V.sub.int at the first stage, so the first driving transistor DTFT 1 is in the on state at the second stage. As shown by a solid arrow in FIG. 5 , the data signal V.sub.data from the data line is transmitted to the second end of the first storage capacitor C 1 , i.e., node B, through the fourth TFT T 4 , the first driving transistor DTFT 1 and the second TFT T 2 which are in the on state, so as to charge node B to be at a potential equal to a difference between the potential of the data signal V.sub.data and the threshold voltage V.sub.th1 of the first driving transistor DTFT 1 , i.e., V.sub.B=V.sub.data−V.sub.th1, thereby to enable a voltage difference between the gate electrode and the source electrode of the first driving transistor DTFT 1 to be equal to V.sub.th1. During this procedure, the first end of the first storage capacitor C 1 , i.e., node A, is always maintained at a potential of the second signal V.sub.dd, so after the charging, node B is always maintained at a potential equal to V.sub.data−V.sub.th1. In addition, the fifth TFT T 5 is in the off state at the second stage, and no current flows through the OLED at this stage. As a result, it is able to prolong a service life of the OLED.

At a third stage, the display driving module 1 in FIG. 2 may be at a display and light-emitting stage. FIG. 3 shows at Stage 3 the signals. To be specific, the control signal V.sub.EM may be a low level signal, the first scanning signal V.sub.Scan1 may be a high level signal, the second scanning signal V.sub.Scan2 may be a high level signal, and the data signal V.sub.data may be a low level signal, so as to enable the first TFT T 1 and the fifth TFT T 5 to be in the on state, and enable the second TFT T 2 , the third TFT T 3 and the fourth TFT T 4 to be in the off state. As shown by a solid arrow in FIG. 6 , the first TFT T 1 and the fifth TFT T 5 are in the on state, so as to enable the first electrode (i.e., the source electrode) of the first driving transistor DTFT 1 to be at a potential of the second signal V.sub.dd from the second signal source, thereby to enable the driving current I.sub.OLED to flow through the first TFT T 1 , the first driving transistor DTFT 1 and the fifth TFT T 5 to drive the OLED to emit light.

Through a saturation current formula for the driving transistor DTFT, the current I.sub.OLED may be calculated as follows:

I OLED = K ⁡ ( V GS - V th ⁢ ⁢ 1 ) 2 = K ⁡ [ V dd - ( V data - V th ⁢ ⁢ 1 ) - V th ⁢ ⁢ 1 ] 2 = K ⁡ ( V dd - V data ) 2 , where V.sub.GS represents a gate-to-source voltage of the first driving transistor, and K is a constant related to a manufacture process and a driver design for the driving transistor DTFT.

As can be seen from the above equation, the operating current I.sub.OLED for the OLED is no longer affected by the threshold voltage V.sub.th1 of the first driving transistor DTFT 1 , but merely relevant to the second signal V.sub.dd and the data signal V.sub.data. As a result, it is able to thoroughly prevent the threshold voltage V.sub.th of the driving transistor DTFT from being drifted due to the manufacture process and a long-term operation, and eliminate an effect of the threshold voltage V.sub.th of the driving transistor DTFT on the operating current I.sub.OLED of the OLED, thereby to ensure a normal operation of the OLED in each pixel unit and ensure the display evenness.

In another embodiment, the display driving module 1 may also be implemented in another circuit structure. As shown in FIG. 7 , the display driving module 1 may include a sixth TFT T 6 , a seventh TFT T 7 , an eighth TFT T 8 , a second storage capacitor C 2 , a second driving transistor DTFT 2 and a third driving transistor DTFT 3 . A first electrode of the sixth TFT T 6 is connected to the data line, a gate electrode thereof is connected to the second scanning line, and a second electrode thereof is connected to a first electrode of the second driving transistor DTFT 2 . A first electrode of the seventh TFT T 7 is connected to a second end of the second storage capacitor C 2 , a gate electrode thereof is connected to the first scanning line, and a second electrode thereof is connected to the third signal source. A first electrode of the eighth TFT T 8 is connected to a second electrode of the third driving transistor DTFT 3 , a gate electrode thereof is connected to the control line, and a second electrode thereof is connected to the anode of the OLED. A gate electrode and a second electrode of the second driving transistor DTFT 2 are connected to the second end of the second storage capacitor C 2 . A first electrode of the third driving transistor DTFT 3 is connected to a first end of the second storage capacitor C 2 and the second signal source, and a gate electrode thereof is connected to the second end of the second storage capacitor C 2 .

The state of the display driving module 1 in FIG. 7 driven by the above method will be described hereinafter in conjunction with the sequence diagram as shown in FIG. 8 .

At a first stage, the display driving module 1 in FIG. 7 may be at a resetting stage. FIG. 8 shows at Stage 1 the signals. To be specific, the control signal V.sub.EM may be a high level signal, the first scanning signal V.sub.Scan1 may be a low level signal, the second scanning signal V.sub.Scan2 may be a high level signal, and the data signal V.sub.data may be a high level signal, so as to enable the seventh TFT T 7 to be in the on state, and enable the sixth TFT T 6 and the eighth TFT T 8 to be in the off state. As shown by a solid arrow in FIG. 9 , the third signal V.sub.int from the third signal source is transmitted to the second end of the second storage capacitor C 2 , i.e., node F, and the gate electrodes of the second driving transistor DTFT 2 and the third driving transistor DTFT 3 through the seventh TFT T 7 which is in the on state, so as to enable the second end of the second storage capacitor C 2 to be at a potential of the third signal V.sub.int, i.e., V.sub.F=V.sub.int. In the embodiments of the present disclosure, the third signal V.sub.int may be a low level signal, so the second end of the second storage capacitor C 2 is reset.

At a second stage, the display driving module 1 in FIG. 7 may be at a discharging and compensation stage. FIG. 8 shows at stage 2 the signals. To be specific, the control signal V.sub.EM may be a high level signal, the first scanning signal V.sub.Scan1 may be a high level signal, the second scanning signal V.sub.Scan2 may be a low level signal, and the data signal V.sub.data may be a high level signal, so as to enable the sixth TFT T 6 to be in the on state and enable the seventh TFT T 7 and the eighth TFT T 8 to be in the off state. The gate electrodes of the second driving transistor DTFT 2 and the third driving transistor DTFT 3 are at the potential of the third signal V.sub.int at the first stage, so the second driving transistor DTFT 2 and the third driving transistor DTFT 3 are both in the on state at the second stage. As shown by a solid arrow in FIG. 10 , the data signal V.sub.data from the data line is transmitted to the second end of the second storage capacitor C 2 , i.e., node F, through the sixth TFT T 6 and the second driving transistor DTFT 2 which are in the on state, so as to charge node F to be at a potential equal to a difference between the potential of the data signal V.sub.data and the threshold voltage V.sub.th2 of the second driving transistor DTFT 2 , i.e., V.sub.F=V.sub.data−V.sub.th2. During this procedure, the first end of the second storage capacitor C 2 , i.e., node E, is always maintained at a potential of the second signal V.sub.dd, so after the charging, node F is always maintained

As can be seen from the above equation, the operating current I.sub.OLED for the OLED is no longer affected by the threshold voltage V.sub.th of the driving transistor, but merely relevant to the second signal V.sub.dd and the data signal V.sub.data. As a result, it is able to thoroughly prevent the threshold voltage V.sub.th of the driving transistor DTFT from being drifted due to the manufacture process and a long-term operation, and eliminate an effect of the threshold voltage V.sub.th of the driving transistor DTFT on the operating current I.sub.OLED of the OLED, thereby to ensure a normal operation of the OLED in each pixel unit and ensure the display evenness.

The fingerprint identification module 2 is configured to, when a finger touches a touch panel, determine concave-convex information about the finger by collecting signals through a processor connected to the signal read line based on a coupling capacitance between concave-convex stripes of the finger and a detection electrode, thereby to obtain fingerprint data of the finger.

In one embodiment, as shown in FIG. 2 or 7 , the fingerprint identification module 2 may include a resetting transistor M 1 , an amplifying transistor M 2 , a switching transistor M 3 , a third storage capacitor C 3 and a detection electrode D. A first electrode of the resetting transistor M 1 is connected to the fourth signal source, a gate electrode thereof is connected to the first scanning line, and a second electrode thereof is connected to a second end of the third storage capacitor C 3 . A first electrode of the amplifying transistor M 2 is connected to the fourth signal source, a gate electrode thereof is connected to the second end of the third storage capacitor C 3 , and a second electrode thereof is connected to a first electrode of the switching transistor M 3 . A gate electrode of the switching electrode M 3 is connected to the second scanning line, and a second electrode thereof is connected to the signal read line. A first end of the third storage capacitor C 3 is connected to the second scanning line. The detection electrode D is connected to the second end of the third storage capacitor C 3 .

The state of the fingerprint identification module 2 in FIG. 2 or 7 driven by the above method will be described hereinafter in conjunction with the sequence diagram as shown in FIG. 3 or 8 .

In the embodiments of the present disclosure, an operating procedure of the fingerprint identification module 2 may be identical to that of the display driving module 1 , i.e., it may also include three stages.

At a first stage, the fingerprint identification module 2 in FIG. 2 or 7 may be at a resetting stage. FIG. 3 or 8 shows at Stage 1 the signals. To be specific, the first scanning signal V.sub.Scan1 may be a low level signal, and the second scanning signal V.sub.Scan2 may be a high level signal, so as to enable the resetting transistor M 1 to be in the on state and enable the switching transistor M 3 to be in the off state. As shown by a dashed arrow in FIG. 4 or 9 , the fourth signal from the fourth signal source, e.g., V.sub.an, is transmitted to the second end of the third storage capacitor C 3 , i.e., node G (a connection point where the second end of the third storage capacitor C 3 , the gate electrode of the amplifying transistor M 2 and the detection electrode D are connected to each other), through the resetting transistor M 1 which is in the on state, so as to enable node G to be at a potential of the fourth signal V.sub.com, i.e., V.sub.G=V.sub.com, thereby to reset node G to be ready for a subsequent signal collection stage. In the embodiments of the present disclosure, the fourth signal V.sub.com may be a signal with a fixed potential, so the amplifying transistor M 2 is in the off state.

At a second stage, the fingerprint identification module 2 may be at the signal collection stage. FIG. 3 or 8 shows at Stage 2 the signals. To be specific, the first scanning signal V.sub.Scan1 may be a high level signal, and the second scanning signal V.sub.Scan2 may be a low level signal, so as to enable the switching transistor M 3 to be in the on state and enable the resetting transistor M 1 to be in the off state.

As shown in FIG. 12 , at the second stage, when a finger touches a touch panel, the fingerprint identification module 2 includes, apart from a reference capacitance C 3 , a detection capacitance Cf generated between the finger and the detection electrode D. Meanwhile, a parasitic capacitance Ct is also generated by the amplifying transistor M 2 itself. A potential at the gate electrode of the amplifying transistor M 2 may be changed along with the detection capacitance Cf (the potential at the gate electrode depends on Cf, C 3 and Ct, i.e., the more the Cf is, the smaller the potential at the gate electrode is, and vice verse), so as to change the current flowing out of the drain electrode of the amplifying transistor M 2 . Hence, it is able for the processor to determine the concave-convex information about a surface of the finger based on the current change, thereby to identify the finger.

The description continues in the full USPTO document.